Fast progress in color reprographic technology combined with a rise of criminal and terrorist activity stimulates the need for new and enhanced security features to be incorporated in financial and identity documents in order to stay one step ahead of counterfeiters.
In early 2000, fraud was at an all-time high. The Bank of Canada's annual report shows that the value of counterfeit banknotes detected in circulation rose from 4.9 million dollars in 2002 to $12.7 million in 2003 (see “Bank of Canada's Annual Report 2003”, Ottawa, Canada, 2003 by R. Goodale). One who deals with security will inevitably have to deal with the issue of counterfeiting, be it in the domain of immigration (passports, ID cards, etc.), credit card fraud, drug trafficking, etc. It is therefore important to continuously innovate in the domain of anti-counterfeiting devices in order to stay one step ahead of present and future counterfeiters. It is also important to inform the general public about such devices. In fact, research has shown that only 1.7 currency security features are known in average, see the paper by H. A. M. de Heij, “A method for measuring the public's appreciation and knowledge of banknotes”, Proceedings of the SPIE—The International Society for Optical Engineering, v 4677, 2002, p 15-55. Contrary to what is generally believed, more and more fake low currency bills are being found, simply due to the fact that most people anticipate that only high denominations are being reproduced, as said in, L. A. DiNunzio, S. E. Chuch, “Evaluating Public Awareness of New Currency Design Features”, Proceedings of the SPIE—The International Society for Optical Engineering, v 4677, 2002, p 1-14.
Most optically variable devices (OVD), see Optical Document Security—Second Edition, by R. van Renesse, Artech House, London, England, 1998, are based on two optical effects: diffraction (Diffractive Optical Variable Image Device) and interference (Interference Security Image Structures, ISIS). The present trend consists of integrating these two effects into one device, as seen in, the paper by A. Argoitia, V. P. Raksha, R. W. Phillips, “Integration of contrasting technologies into advanced optical security devices”, Proceedings of the SPIE—The International Society for Optical Engineering, v 5310, n 1, 2004, p 299-311.
In the case of ISIS, there is still much opportunity for innovation. Interference is an interesting effect for it offers a color change upon tilting the device. Consequently, it is impossible to recreate this effect by a simple photocopy, photography or any reprographic process. This feature is very important considering the fact that introduction of high quality inexpensive printers has had a direct effect on the number of false bills in circulation. In 1995, less than 1% of counterfeited bills in the U.S. were digitally fabricated, compared to almost 40% in 2002, see the paper by L. A. DiNunzio, L. Clarke, “The new color of money: safer, smarter, more secure”, Proceedings of the SPIE—The International Society for Optical Engineering, v 5310, n 1, 2004, p 425-439. The first ISIS device of this type was developed at the National Research Council of Canada, see the article by J. A. Drobrowolski, F. C. Ho and A. Waldorf, “Research on thin film anticounterfeiting coatings at the National Research Council of Canada”, Applied Optics, Vol. 28, No 14, 15 July 1989. The original design consisted of 13 dielectric layers, offering a gold to green color shift. For economic reasons, over the years, the number of layers was brought down to five and later to three by using metallic layers.
Another example is optically variable ink which is being used on many international currencies (over 40 countries) as described in the article by R. W. Phillips, and A. F. Bleikolm, “Optical coatings for document security”, Applied Optics, Vol. 35 and R. W. Phillips, and M. Nofi, “Colors by Chemistry or by physics?”, Society of Vacuum Coaters, 42nd annual technical conference proceedings, 1999. No. 28. 1996. This ink has also been combined with magnetic elements as described in the paper by T. Jagielinski, “Magnetic Imaging of Currencies and Secure Documents”, Proceedings of the SPIE—The International Society for Optical Engineering, v 4677, 2002, p 159-168. and P. G. Coombs, V. P. Raksha, T. Markantes, “Overt and covert verification via magnetic optical security devices”, Proceedings of the SPIE—The International Society for Optical Engineering, v 4677, 2002, p 182-193.